This project addresses a major goal to identify HIV-1 antagonists that could inactivate the virus specifically before host cell encounter. Inhibition of he initial entry of HIV-1 into host cells remains a compelling and yet elusive means to prevent infection and spread of the virus. Entry is dependent on the ability of the virus envelope protein spike to interact with specific cell receptors in a multistage process that triggers conformational rearrangements in Env and consequent fusion of virus and cell membrane to deliver virus contents to the host. A peptide triazole class of entry inhibitors has been identified previously and found to be able to bind to HIV-1 gp120 with nanomolar affinity, to suppress protein ligand interactions of the Env protein at both its CD4 and co-receptor binding sites and to inhibit cell infection by a broad range of virus subtypes. Strikingly, we have found recently that a multivalent form of the peptide triazole KR13 displayed on gold nanoparticles (AuNPs) is able to disrupt virus particles in the absence of host cells, causing leakage of the internal protein p24 and exhibiting strong antiviral activity. We hypothesize that the multivalent peptide triazole AuNPs are capitalizing on the intrinsic metastability of the virus Env, and that optimizing such nanoassemblies based on modulating their fundamental properties can help identify HIV-1-specific virucidal agents to use in AIDS treatment and prevention by promoting cell-free virus rupture and inactivation. Based on these findings, the Specific Aims of this proposed project are to (1) determine rules of spatial geometry and surface rigidity of gold nanoparticle - peptide triazole (AuNP-PT) that promote cell-free HIV-1 virolysis; (2) determine mechanistic properties of AuNP-PT induced HIV-1 virolysis and its relationship to the pathogenic process of virus cell infection; (3) establish fundamental stability and cell transport properties of AuNP-KR13 nanoconstructs. Overall, this work will derive principles for designing multivalent Env-targeting NP's to enable virucidal actions that are specific for HIV-1. The NP's will help expand understanding of the extent to which the Env metastability that is critical for pathogenic host cel entry can be hijacked to develop tools for HIV-1 therapeutics and microbicides. The results will provide precedent for how other gp120 inhibitor-NP compositions can be devised for HIV-1 virus inactivation as well as how ligand-specific pathogen rupture can potentially be achieved for other viruses that contain metastable prefusion surface protein complexes.